You've just highlighted an important lesson... diligence.
Easy to "not pay close enough attention" or to be distracted and regret it. Been guilty of the same more times than I care to admit.
Speaking of "diligence and paying attention".... I recall a few years ago when I missed a significant bottom. The markets were "apparently just bopping/chewing around" when I got a call from my dentist about an opening in their schedule and asked if I would like to take the spot for my routine cleaning. Seeing that the market "wasn't doing much", I said "OK". Dentist is about 5 minutes from my house... and I was back within about 90 minutes. In the mean time, the market made a bottom and the ES bounced ~ 100 points. Can't tell you how much that "lack of discipline about tending to the market" pissed me off! DAMNED expensive cleaning!